Field of the Invention
The invention relates to an active bearing for the controlled vibration transmission between a vibrating load and a support unit. The active bearing chiefly serves for the vibration reduction, that is the vibration damping and/or vibration decoupling and/or for the vibration compensation of the vibrating load with respect to the support unit. The active bearing is also capable of influencing the vibration state of the vibrating load.
For this purpose, the active bearing comprises an interface to be fitted to the load to be borne with the attributable static and dynamic load transfer acting on the bearing via the interface. To support the static load transfer, typically caused by the weight force of the load, at least one support element in an operative connection with the interface and the support unit is provided with the support element forming a first force path. Furthermore, there are provided at least one linear actuator supported indirectly or directly on the support unit, a gear unit for the path transmission of an actuating path change or an actuating path originating from the linear actuator. The gear unit is in an operative connection with the at least one linear actuator, as well as at least one decoupling unit, which serves for the decoupling of the static load transfer and for transmitting the dynamic load transfer and by means of which the gear unit is indirectly or directly in an operative connection with the interface. The at least one linear actuator, the gear unit and the at least one decoupling unit are disposed in a serial sequence and form a second force path, which is typically orientated parallel with the first force path, for the dynamic load transfer.
Description of the Prior Art
In numerous technical applications, mechanical structures are caused by machines to vibrate in an undesirable manner. In order to reduce the transfer of the exciting forces to the mechanical structures, the sources of interference, for example in the form of engines or other units, are mounted elastically in many cases. In order to avoid the vibration amplitudes acting on the elastic bearings becoming unacceptably great, such bearings have a sufficiently high damping capacity, which however can in turn have a negative effect on the capacity for vibration decoupling. This conflict exists in the case of elastic bearings ultimately leading to a compromise between the highest possible damping of vibrations in the low frequency range and the lowest possible damping vibrations in the higher frequency.
A known bearing topology solving the aforementioned bearing problem comprises a flexible element, for example in the form of a spring, introduced between a load and a support unit, parallel to which a series arrangement comprising a largely flexible as well as a largely damping element is incorporated. A technical embodiment of such a bearing topology is represented by a hydrobearing described in EP Patent 2 253 863 A2, which provides an interface serving for the load application and a support unit, which are both connected via an elastic support element and, together with a dividing wall, form the boundary of a working chamber filled with a fluid. By means of a damping channel provided inside the dividing wall, the working chamber is connected in a fluid-communicating manner to a compensating chamber, which together with the dividing wall is surrounded by an elastically flexible boundary wall.
Hydrobearings of this kind are used primarily in motor vehicles to damp or to insulate the vibrations occurring during operation. The elastic support element, which is made from a highly elastic rubber, provides for the acoustic insulation, whilst the damping is achieved by a resonance effect in the damping channel, which connects hydraulically the working chamber with the compensating chamber.
A further embodiment for an elastic bearing provides for the integration of at least one suitably controllable actuator, so that the disturbing vibrations transferred by the load onto the bearing are compensated for as completely as possible by counter-vibrations generated by the actuator and introduced into the bearing. The control signals required for the actuator control are determined from measured variables with the aid of a suitable control strategy. The sensors required for this can be located both in the bearing and also outside the bearing. Depending on the control strategy, use is made of force, path, speed or acceleration sensors, microphones or other techniques. A preferred control strategy for vibration decoupling or compensation provides for the targeted actuator-led introduction of counter-vibrations in respect of the disturbing vibrations acting at the load side on the bearing. In order to be able to embody the actuator required to this in the easiest, smallest and most cost-effective manner, the at least one actuator initiating the counter-vibrations should be decoupled from the static load transfer, which essentially is caused by the weight force of the load in question, so that only dynamic loads caused by the disturbing vibrations act on the at least one actuator.
An active bearing technically embodied in this way is described in DE 10 2008 055 535 A1. Here, it involves an active damping hydraulic bearing, preferably for use as an engine bearing for a motor vehicle, which comprises a working chamber which is connected via an annular channel to a compensating chamber. In order to damp low-frequency vibrations from the engine with respect to the bodywork to be relieved of vibrations, hydraulic fluid flows out of the working chamber via the annular channel into the compensating chamber and back. If, on the other hand, high-frequency vibrations are introduced into the engine bearing, the annular channel is closed dynamically. To insulate high-frequency disturbing vibrations between engine and bodywork, a membrane partially bounding the working chamber is deflected with the aid of an actuator, so that the volume of the working chamber is kept as constant as possible despite the effect of high-frequency vibrations into the engine bearing. A piezoelectric linear actuator is used to deflect the membrane with the small actuating paths of the linear actuator being converted with the aid of a path transmission mechanism into large actuating path changes of the membrane, so that the membrane can cover large paths and compensate for large volumes in the working chamber. Depending on the control of the linear actuator, compensation for disturbing vibrations acting on the active hydrobearing can thus be obtained.
A further damping arrangement is disclosed in publication DE 41 16 270 A1, which provides a support element, a path transmission mechanism, an actuator, an elastomer element and a damping unit along a single force path, comparable with an arrangement such as is described immediately above; the devices differ solely in the embodiment of the damping unit.
A decoupling arrangement in the form of a hydraulic motor bearing for use in the motor vehicle sector is described by publication DE 196 17 840 A1. Such engine bearings are referred to as hydrobearings and are characterized by two working chambers filled with hydraulic fluid, which are in an operative connection via a transfer channel. In addition to the generally known form, the bearing comprises a further chamber, which is filled with electro-rheological fluid (ERF). The viscosity of this fluid can be influenced by applying a voltage. By regulating the viscosity of the ERF, the dynamic properties of the bearing can be changed in a targeted manner and dependent on the given operational state. The use of ERF, however, enables only the change in the bearing properties, in particular the stiffness and the damping, but not the transfer of additional forces that counteract the disturbing vibrations.